Electrical measurements of the equilibrium np product (n2ie) in heavily doped n- and p-GaAs were performed. The n2ieD product (where D is the diffusivity) was measured by fitting the collector current-voltage characteristic of a homojunction bipolar transistor to an ideal diode equation modified... mehr

Understanding of the raised beach and other interglacial sequences in the southern part of the British Isles has been improved through use of the amino acid racemization technique. This method has permitted correlation of these isolated and fragmentary marine deposits1,2 which, except for the... mehr

VOLCANIC rocks from subduction settings frequently contain 10Be enrichments that have been attributed to sediment subduction1–6, and are often characterized by (238U/230Th) ratios greater than unity, in contrast to mid-ocean-ridge and ocean-island basalts7,8. Here we report such an excess of... mehr

Summary The nature of the association of U1 RNA with rapidly sedimenting RNP structures in rat hepatoma nuclei was investigated. The effects of salt and proteinase K treatment on the stability of this ‘bound’ form of U1 RNA were studied using sucrose density gradient analyses. Quantitation of... mehr

Abstract 18O/16O, 34S/32S, and D/H ratios as well as vacuum-fusion H2O+ contents were measured for late Tertiary volcanic basaltic rocks ranging in composition from quartz tholeiites and alkali olivine basalts to melilite-bearing olivine nephelinites and for peridotite xenoliths from the Northern... mehr

A tunnel diode was formed from GaAs containing excess arsenic incorporated by molecular beam epitaxy at reduced substrate temperatures. The incorporation of excess arsenic during growth results in a more efficient incorporation of silicon on donor sites and beryllium on acceptor sites. The better... mehr

An interferometer for broadband single-cycle THz pulses is developed based on the Michelson configuration. Total internal reflection of THz pulses in high-resistivity silicon prisms provides a nearly 180° phase shift of one arm relative to the other to achieve destructive interference. We show... mehr

The effects of degenerate Fermi statistics on electron injection currents for p+-GaAs grown by molecular beam epitaxy are presented. To achieve Be dopant concentrations of greater than 8×1019 cm−3, the substrate temperature during growth was reduced to approximately 450 °C from the usual 600... mehr

We present experimental evidence that minority electron transport across a thin, quasineutral p+ GaAs region is limited by the thermal velocity of the electrons rather than by conventional diffusive transport. A set of GaAs homojunction np+n transistors with base widths of 4000, 2000, 1000, and... mehr